摘要:

ABSTRACT.Freeze‐cleave replicas of encysted cells of the myxamoebae ofPhysarum polycephalumwere examined to determine the intrawall substructure and to compare the intramembrane structural components. Cleaved areas of the cyst wall revealed a laminated substructure devoid of the macromolecular interruptions (intramembrane particles or IMP) visible in the cleaved cell membranes. The cyst wall adjacent to the cell membrane appears laminated, and a loose branching network of fibers and fibrils occurs at the wall periphery. The absence of intrawall particles is interpreted as a lack of protein or polypeptide components, thus suggesting additional support for the conclusion that polysaccharides are the major wall constituents. When cleaved cell membranes of encysted cells were examined, more intramembrane particles per unit area were observed on the extracellular membrane leaflet than on the protoplasmic membrane leaflet. In addition, homogeneous as well as aggregated particle distributions were visible on cleaved membrane leaflets. Moreover, the presence of aggregated and unaggregated particles on the same membrane leaflets similarly suggests asynchrony of the cell population. This paper examines and compares biological processes involving the cell membrane that may be related to different stages in the cell cycle or to periods of temporary stasis during the cell cycl

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05412.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.Freeze‐fracture techniques reveal differences in fine structure between the anterior three flagella ofTritrichomonas foetusand its recurrent flagellum. The anterior flagella have rosettes of 9–12 intramembranous particles on both the P and E faces. The recurrent flagellum lacks rosettes but has ribbon‐like arrays of particles along the length of the flagellum, which may be involved in the flagellum's attachment to the cell body. This flagellum is attached to the membrane of the cell body along a distinct groove that contains few discernible particles. Some large intramembranous particles are visible on the P face of the cell body membrane at the point where the flagellum emerges from the cell body. The randomly distributed particles on the P and E faces of the plasma membrane have a particle density of 919/μm2and 468/μm2respectively, and there are areas on both faces that are devoid of particles. Freeze‐fracture techniques also reveal numerous fenestrations in the membrane of the Golgi complex and about 24 pores per μm2in the nuclear

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05413.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.Studies of the bristle (dorsal) cilia ofEuplotes minuta. E. aediculatus, andStylonychia mytilusby light and electron microscopy indicate that these cilia do not beat metachronously in any of the species. The bristle cilia inStylonychiamay beat actively, but those inEuplotesstand erect or are bent in different directions with the flow of water. The duration and degree of bending appear correlated with the duration and velocity of the water current. The fine structure of the bristle complex is similar in bothEuplotesspecies and like other reports ofEuplotesin the literature. The complex consists of paired kinetosomes, the anterior bearing a short cilium containing four to six rows of fibrous balls (lasiosomes) oriented along the anterior surface of the axoneme, the posterior lacking a cilium but with a small cap. Microtubular ribbons are associated with the paired kinetosomes, and a collar with a pronounced alveolar ring underneath the pellicular membrane tightly surrounds the cilium at the opening of the bristle pit. The bristle complex inS. mytilusdiffers from that ofEuplotesand other hypotrichs in that it has a single kinetosome in interphase cells and, attached to the kinetosome, a prominent fibrous structure (parakinetosomal body). Microtubules are attached to the parakinetosomal body. As inEuplotes, the bristle unit is surrounded by mucocyst‐like organelles (ampules). Observations of behavior and fine structure suggest that the dorsal bristles may be sensory, perhaps responding to stimuli from water currents, although other functions are possible, to

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05414.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.Various ions and treatments known to alter the availability of free Ca2+were examined with respect to their effects on the cytopharyngeal pouch, a large prey receptacle found in the potentially carnivorous macrostomal form ofTetrahymena vorax.Addition of Ca2+, Ba2+, or Sr2+induced the pouch to separate from the region of the cytostome, forming a large empty vacuole. Na+, alone, had no effect, but lowered the concentration of Ca2+required to produce maximum vacuolar formation in populations of cells. Vacuolar induction was also initiated by the cation ionophore A23187 or by subjecting macrostomal cells to an electric current. In the presence of divalent cation chelators EDTA and EGTA, the cytopharyngeal pouch collapsed and was resorbed. Taken together, these results suggest that Ca2+plays an important role during phagocytosis in this cell type.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05415.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.The sequence of formation and ciliation of basal bodies and the subsequent organization of compound ciliary structures of the oral apparatus ofTetrahymena thermophilawas reanalyzed with the aid of scanning electron microscopy of cells in which the epiplasmic layer was exposed, as well as by light microscopy of protargol‐impregnated specimens. This combination of methods allowed the delineation of numerous steps in the patterning of the oral ciliature, some of which have received little or no previous attention. Highlights include: the initial formation of “strings” of nonciliated new basal bodies in juxtaposition to relatively few basal bodies of the stomatogenic kinety; generation of basal body pairs, roughly oriented along the anteroposterior axis of the cell, that later align side‐by‐side to assemble promembranelles; condensation and reorientation of promembranelles simultaneous with addition of a third row of basal bodies anterior to the original two rows; production of a very short fourth row of basal bodies at the anterior right end of each developing membranelle; generation of the outer basal body row of the undulating membrane (UM) after alignment of the inner row, with transient ciliation of the inner row preceding permanent ciliation of the outer row; limited basal body resorption at the ends of membranelles; and sculpturing of the right ends of membranelles by a movement of basal bodies associated with formation of the ribbed wall adjacent to the UM. In the old anterior oral apparatus a repetition of the processes of generation of a new outer UM row and sculpturing of right ends of membranelles takes place in synchrony with the corresponding events in the oral primordium, following prior shedding of the old outer UM row and loss of the sculptured pattern in association with temporary regression of the ribbed wall micro‐tubules. Oral development is complex, with different processes involved in the assembly of the membranelles and the UM, and with a sequence of distinct events involved in the generation of each of these structures. Speaking comparatively, membranelle development follows the same pathway in many, perhaps all, ciliates in which these structures or their homologues develop from a common stomato

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05416.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.Extraction of the ciliated protozoonTetrahymenawith nonionic detergents produces a surface‐related cytoskeleton that consists of a basic lamina of whole‐cell dimensions together with associated microtubule and microfilament systems, including all ciliary basal bodies. The organization of the isolated cytoskeleton has been studied using scanning electron microscopy, and several new features are described in the oral region. Here the ciliary basal bodies are arranged in a very stable and highly complex pattern. This pattern was found to be identical in the four species ofTetrahymenawe examined. In addition, various microtubular bundles and two separate systems of filaments were observed in scanning electron micrographs of isolated oral skeletons. The appearance of the deep fiber bundle in preparations of this type suggests that it arises, at least in part, as an extension of the ribbed wall microtubules. On the basis of its distribution within the oral skeleton, one of the filament systems described is suggested to be a contractile system responsible for pinching off food vacuo

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05417.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.Activity of ornithine decarboxylase, the major rate limiting enzyme of polyamine biosynthesis, was determined in bloodstream trypomastigotes ofTrypanosoma brucei brucei.The enzyme required pyridoxal‐5′‐phosphate, dithiothreitol and EDTA for optimal activity. Several properties of the enzyme were investigated and compared to the mammalian enzyme. Most notably, the parasite enzyme was>60‐fold more sensitive to the inhibitor DL‐α‐difluoromethylornithine than its mammalian counterpart, thus making it an attractive target for

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05418.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.The multiplication rate of “wild‐type” (WT) populations ofAcanthamoeba castellaniiwas inhibited 50% by ∼3 μg otigomycin/ml; OliR2an oligomycin resistant cell line, required ∼27 μg/ml for the same inhibition. ATPase solubilized from OliR2mitochondrial fractions required 3–10‐fold higher concentrations of oligomycin than did identical WT fractions to achieve 50% inhibition of activity. Resistance was correlated with altered mitochondrial ATPase sensitivit

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05419.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.The electrophoretic mobility of six isoenzymes from 10 species ofCrithidiafrom insects were compared. Five zymogram patterns emerged. Pattern I was presented byC. acanthocephaliandCrithidiasp. fromEuryophthalmus davisi; pattern II byC. hutneriandC. luciliae thermophila; pattern III byC. arili; pattern IV byC. luciliae luciliae, Crithidiasp. fromAedes solicitans, C. harmosa, andC. fasciculata; pattern V byC. oncopelti.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05420.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

ABSTRACT.Dehydrogenase activity with hydroxysteroids has been observed inTetrahymena furgasoni(formerlyT. pyriformisstrain W), and the enzyme responsible has been isolated from this organism. The purified dehydrogenase is active with a variety of steroid alcohols at apparent Kmvalues ranging from 0.2 to 4.0 mM. The C‐3 hydroxyl of ring A of the steroid nucleus is the preferred position of oxidation. However, a variety of other secondary alcohols are also substrates, with apparent Kmvalues for 2‐butanol, 2‐pentanol, and cyclohexanol of 880, 1000. and 150 mM, respectively. With both steroidal and nonsteroidal alcohols. NAD is the preferred co‐substrate, although low activity with NADP is observed. Evidence is presented that the activity with secondary alcohols, whether steroidal or not, is the property of a single protein

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1982.tb05421.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY